Beneath every home, hill, and aging sidewalk in Oakland, the forces that shape the contours and history of the place we call home are steadily at work. As is Andrew Alden, a geologist who has taken it upon himself to study those forces and publish his findings.

Alden has run the blog Oakland Geology for more than a decade, chronicling the nature of the rocks and hidden machinations that he believes have had a significant hand in authoring the town’s history. After spending 10 years exploring every single block in Oakland and then writing a book about what lies beneath our feet, his publisher asked him to start over and write about the human dramas that have unfolded above ground as a result of our topography. That book is Deep Oakland, which Alden hopes to release next summer. 

The Oaklandside spoke with Alden about his blog, forthcoming book, and how Oakland’s geology shapes life in The Town. The interview has been edited for length.

Your blog, Oakland Geology, chronicles just that—the geology of this town, which you’ve called home for 33 years now. What was the impetus behind starting the blog?

Well, when I moved to Oakland it was 1989. Two weeks later, the Loma Prieta earthquake happened, which was a pretty exciting way to be introduced to a city. I started the blog quite a bit later, in 1997. We were all getting online at the time, you know, the web was new. And I had been doing stuff online on bulletin boards like The Well, where I’ve been for a very long time, since the early 90s. I took it upon myself to get into sidewalk stamps. These are the concrete marks that you see on a sidewalk from people who make the sidewalks. There’s a million of them in Oakland and Berkeley and Hayward—any place with old sidewalks. 

So I set out to explore every block of Oakland. I did that. It took me about 10 years. I thought, well, this is great preparation to write about Oakland because I’ve set foot on every part of Oakland while I was doing that. And that became the blog Oakland Underfoot, an older sibling of Oakland Geology.

How did your interest in geology first begin? Was there a point where you decided to make this a serious part of your life?

I’ve always had a fascination with landscape, with topography, but I picked geology for a major in college because it seemed less demanding than other sciences. In some ways it is, but in others, it’s endlessly complex. Earth science touches on every other branch of science. In fact, I consider geology to be the mother science of physics and chemistry, and it should be taught first in schools, but don’t get me started.

What kind of equipment do you use in your studies?

I walk around with my phone’s camera and compass, a hand lens, and a little bottle of hydrochloric acid with an eyedropper. That’s the best way to detect limestone or calcium carbonate minerals—they fizz. I’m guided by a geologic map of the Oakland region that was issued in 2000 by the U.S. Geological Survey. I used to carry a rock hammer, but I’ve decided I don’t want to damage our rocks even though no one would notice. I know them all by heart.

You say that the hills are full of a multitude of rock types and that they “come from places near and far.” Can you explain how that’s possible?

The rocks in the hills formed in different places at different times, from the Jurassic to the Miocene periods, or in ordinary English about 165 million to about 9 million years ago. Plate tectonics was moving them around the whole time, to put it briefly, rearranging western North America. Most recently, like within the last couple million years, pressure [across] the Hayward Fault has pushed up the hills, where erosion has exposed the whole mixed assemblage. It appears to me that Oakland has more variety in its rocks than any other American city.

Where can people go to touch some of the youngest naturally occurring rocks in Oakland? Some of the oldest? 

The young volcanic rocks along the north end of Grizzly Peak Boulevard are 9-10 million years old. They’re pretty fresh. The old volcanic rocks in Leona Heights, exposed along Campus Drive and in the city’s Leona Heights Park, were born some 165 million years ago and have gone through serious changes since then as plate tectonics carried them around.

How far would we have to turn back time before the topography and formal landscape of Oakland (the hills, the canyons, the lake, the shore, etc.) would be unrecognizable?

This has two answers. The Hayward Fault is steadily carrying everything west of Montclair to the north, so going back a million years or so, which isn’t very long for a geologist, would leave the area similar to today but unrecognizable in detail. The other answer is that during that same time, we’ve gone through about 10 ice-age cycles. During the coldest phases of these ice ages, the sea level was roughly 400 feet lower, about the same as the height of Oakland’s tallest buildings. At these times the entire San Francisco Bay was a dry valley, Lake Merritt was a deep ravine, and there was no shore.

The lake is a huge part of Oakland’s character, but I don’t think many people know too much about its human history. Can you speak a little about that?

Lake Merritt was very useful to the Ohlones, you know, they’d harvest shellfish, they’d go in the marshes and pick reeds for their baskets then go fishing, hunting waterfowl, and so on. But it was this neat avenue they could take. They had a nice village in Trestle Glen, and at high tide, they could take their boats all the way out to the bay and travel to the oak groves on Alameda and do their business. And it was also really good access to go up into the hills at different times of the year. 

But when the Spanish showed up and they started exploring, they said, “What’s this goddamn slough doing here? We’re trying to get an expedition going here.” [The Spanish] had to go out of their way and wander up and down through the hills in Cleveland Heights and the hills above Grand Lake. They hated the slough, they didn’t like it at all. It was just something to get around. And then when the Americans showed up and founded “Oakland” and when they founded what became the town of Brooklyn (1856-1872) on the other side of the slough, the slough was nothing, you know, it was just this thing that was in the way. And the city grew around it and, at first, they just threw all their sewage into it. 

Around 1880, all the town’s doctors wrote a letter to the city that said, “This place called Lake Merritt is terrible.” They called it Lake Merritt because Samuel Merritt, one of the early mayors of Oakland, put a dam across it. So it turned from a tidal slough to a sort of tidal lake. And the reason he did it was so that he could turn his landholdings into nice mansions. And you know, sure enough in the 1880s and 90s, Lake Merritt was surrounded by gracious homes. And the last one of those remaining is the Camron-Stanford house. 

But eventually, the city just bought all the shoreline and said, you know, “We’re gonna dredge this disgusting slough. We’re gonna dredge it all out and make it a nice lake, a nice ornamental pool, and we’re gonna build up the shore.” All that was done in the 1910s. The lake is completely different now, it has a completely different purpose than what it was before.

And one thing we did was we kind of rearranged history because in 1870, Samuel Merritt (when he dammed the lake) also got his friends in Sacramento to pass a law that outlawed hunting and fishing around Lake Merritt. That was all so that he and his friends could develop the land. Well, nowadays, we say that in 1870, Lake Merritt was established as the first bird sanctuary in America, and the first wildlife refuge in the world. That’s kind of a manufactured story. 

I don’t begrudge anyone for saying it because if you look at the lake today it’s a wonderful thing, a product that had unintended consequences that we are enjoying today. But it was actually passed just to keep the duck hunters from spraying all the bystanders with birdshot, and that’s what they did. They’d row in and shoot ducks and then roll back to San Francisco and sell for a buck a piece. 

And this is the type of history that readers can expect to encounter in your forthcoming book, Deep Oakland?

Deep Oakland [is] kind of a survey of the city of Oakland: the early days, when people first showed up here. They looked around, the way everyone does, the way all the pioneers did everywhere they went, and they would say, “What can I make a living from? What kind of businesses can I start? What kind of deals can I make? What’s here?”

Some of the things they discovered here in 1850 were a great site for a seaport, and great places to start farming. And when they poked around in the hills, they found great bedrock, and they said, “You know what, I can start a quarry, I can make crushed stone for the people down in the town who are making concrete, who are building foundations who are building the harbor.” 

And so they did that. And that was kind of a synergy—that Oakland sort of spun itself up from nothing, sort of the same way San Francisco did. They showed up because there was a harbor and they looked around and they did the same thing. They saw that there’s rock here, and they chewed it up, all the hills, with rock quarries. 

And why are there rocks here? Why is there this weird little slough that we call Lake Merritt? What did it look like then? How did the city change it? Why is it so unusual looking, and why is it here? Geologists have answers to these things. For example, downtown is on a beautiful platform of sand because it was made that way in the ice ages. 

I just got deeper and deeper into it, and every part of town has a geological story. Real estate developers, 100 years ago, before we had universal water supplies or plumbing or anything like that, said, “Oh, this site has great drainage. You’ll have your own sewage cistern and your own well. These are great spots for your nice home.” That’s a whole viewpoint we don’t have anymore in real estate. So things have changed, and that’s kind of what I’ve been focusing on. It’s been delightful to research, poking around old newspapers.

How has the geology of Oakland contributed to the distribution of wealth across town?

Lake Merritt used to be a very desirable district because it’s a healthy place, it’s got good breezes and it’s near downtown. You can have excellent landscaping there. That’s why it was an upper-class place. And then upper-class homebuilders moved up into the foothills after that, and by the foothills I mean, the low hills around the Maxwell Park neighborhood. They’re on [the southwest] side of the fault—they’re low hills, a few hundred feet high, but they have excellent scenery and catch the breeze. And the developers would run streetcar lines up to them. So you could build your house and ride the streetcar to San Francisco on the ferry. 

But it all stemmed from the topography, and that’s why the premium neighborhoods are still that way—because they started out that way, 100 years ago, and have maintained it all these years. The lower-income developers moved to the flats, which, when land opened up, had started out with farms. They then moved to industries, because the industries would sink wells for their water supply—that’s why they were there, for the good water supply down in the flats. And then when the water ran out, the industries moved out because things got cheaper out of town, and the land became available for more inexpensive housing. 

That’s why the East Oakland flats are the way they are, and the North Oakland flats. West Oakland was a little different because it’s on the same platform as the old downtown, so it was settled much earlier. That’s why it’s so full of these wonderful Victorian houses. The railroad made that neighborhood wealthy.

Then, finally, the high hills became available when everybody got cars in the 1920s. All the landowners who owned the hills bought them as speculation and as watershed land. They were gonna have water companies up there. And all that fell through, but they said, “Well, okay, now we have cars. We can develop subdivisions in a whole different way. We don’t need trolleys anymore. We don’t need the ferry.” And that’s why they developed the way they did. History intersected with topography. That’s the story of Oakland.

You describe your upcoming work Deep Oakland as an “odd book.” What do you mean by that?

No one has written a book like it. Like I was saying, the choices that different people have made here, from the Ohlones to the Americans, depended on facts in the landscape that each have a geological story. Nobody I know of has braided those two strands of history, human and geological, the way I’ve done. If I lived anywhere else, I’d explore it just as thoroughly, but in exploring Oakland I found unexpected depth in its geology and universal lessons in its human history. I think that many cities could support books like Deep Oakland, and I hope other writers will write them. But Oakland is really special and deserves to be the first.